Threading with A B phase only?

Ah I didn't know that thanks. Did you get the Wantai 2H Microstep Drivers (DQ860MC) with your 1090oz/in, steppers? Those same drivers are offered as a package with their 1600 oz/in NEMA34's....

Andy thanks but I think I'd prefer to be a sheep and keep it simple and use ordinary stepper motors like others do, at least then it is easier to bleat for help! The Encomat 20E is 8" x 40" or in America terminology I think 16" x 40". Other Andy of Mtndrew77 was saying that the main leadscrew feed was a little slow with NEMA34 1090 oz/in and could be speeded up by upgrading with a more efficient ball screw, hence i am thinking simpler just to up the power - their NEMA34 1600 oz/in is not really much more expensive and comes with the same drivers.

A 1600oz/in NEMA-34 motor may not be any faster than a 1090oz/in NEMA-34 motor. In fact, all other things being equal, it will more than likely be slower. (It will only be more powerful at or near 0 speed.)

Ah well thank you both of you - this is all a very interesting learning process for me and I am grateful for your advice. So what is the advantage of a more powerful motor?? I am thinking more power on the longitudinal axis enables heavier cuts and smoother threading....albeit as you now tell me not faster?

Sorry for the confusion. If you want better performance the key will really be the ballscrews. This machine was never designed for full contouring only one axis motion at a time thats how they got away with using leadscrews. Just having a bigger or faster motor really won't help you. The problem with moving faster with the leadscrew is backlash; when you change directions at a much higher speed it just sounds horrible and is really hard on the machine. A more powerful motor really won't help you much either because the machine wasn't really designed for heavy cutting. If you push it to hard you will just end up pulling the headstock out of alignment. The nema34 1600oz should work fine and will probably give you about the same performance. The DQ860MC drive is the same one I have, and so far its performed pretty well. Also keep in mind when using leadscrews you will have to plan you toolpath to avoid direction changes while cutting. If you don't you will end up with gouges in your part.

Ok understood thanks Andy.

My latency test gives a figure around 50k-60k - not very good but is that about as good as i can expect from a Dell Optiplex 760 with Intel core 2 duo 3ghz, 4 gb RAM, Intel integrated graphics? If so, then I suppose slow leadscrew is going to be better for me than quick....Are there some tweeks in wheezy that will bring the latency down or is the only thing to get a separate graphics card installed?

There's a ton of info here wiki.linuxcnc.org/cgi-bin/wiki.pl?Latency-Test, but the Mesa card generates the step pulses so you shouldn't have an issue

Oh that's good thanks. I have done all the bios stuff (disabling power saving features, virtualization, etc). When I disable multi-core processing to have only one of the duo 3ghz cores operating, the latency dropped significantly from 26000 to 20000 (1.0 ms) & 60000 to 30000 (25 us) which is interesting. Anyway I am ordering two NEMA34 1090oz steppers and drivers same as yours. Thanks again. Adam